A suspending apparatus for a vehicle functions to support the vehicle body and to buffer vertical motions of the wheels due to uneven road surfaces or the like, thereby preventing the propagation of vibrations, to the vehicle body. Further, the suspending apparatus functions to suppress irregular vibration of the wheels, thereby stabilizing the running state. On the other hand, the suspending apparatus also functions to propagate the driving force, braking force, lateral force, and the like which are caused between the wheels and the road surface, thereby keeping a desired running performance.
Such suspending apparatus for vehicles has been disclosed in, for instance, JP-B-62-50339. According to such apparatus, the subframe is not fixed to the frame of the vehicle body and the side-sill, thereby making it difficult to propagate the vibration from the road surface to the vehicle body, and when the vehicle collides, the shock force which is input from the rear bumper is transferred to the vehicle body frame, thereby improving the safety of passengers in the rear seat.
On the other hand, there is also known as shown in FIG. 21, a suspending apparatus for vehicles which is constructed in a manner such that a suspension arm 1006 comprises a wheel supporting portion 1028 connected with the side of a wheel 1004 and first and second vehicle body side supporting portions 1034 and 1036 connected with the side of a vehicle body 1002. The wheel 1004 is coupled with the vehicle body 1002 by the suspension arm 1006 such that it can be vertically oscillated or reciprocated.
Some vehicles use an independent suspension system in which the right and left wheels are respectively independently suspended. There are various types of independent suspension systems, such as the swing axle type, wishbone type, strut type, and the like. Particularly, according to the strut type, a shock absorber comprising inner and outer cylinder members is used as a part of a suspension link. The lower end of the shock absorber is connected to a lower arm, and the upper end is connected to the vehicle body, whereby the shock absorber prevents propagation of vibration from the wheel to the vehicle body.
Such a suspending apparatus for vehicles has been disclosed in JP-B-61-48443. According to the suspending apparatus for automobiles disclosed in this publication, a lower suspension arm is integrally formed by first and second arm members and is provided in a ball joint attaching portion, the upper wall portion of the first arm member is downwardly lowered and a flat plate-like extending portion is joined to the lower surface of the second arm member to thereby form a closed cross sectional structure, and proper strength can be provided in consideration of the load which is applied to each portion of the suspension lower arm. The weight can be also reduced.
Another known suspending apparatus for vehicles is shown in FIG. 29. In FIG. 29, reference 2002 denotes a knuckle and 2004 indicates a wheel shaft. A wheel hub 2006 is attached to the wheel shaft 2004. A wheel 2010 to which a tire 2008 is mounted is attached to the wheel hub 2006. The knuckle 2002 is supported by a suspension arm 2012. The suspension arm 2012 is formed in an almost A-shape. A supporting portion 2012a of the arm 2012 is attached to a supporting arm 2014 of the knuckle 2002. Supporting portions 2012b and 2012c of the arm 2012 are attached to a vehicle body (not shown) by brackets 2016. Thus, the suspension arm 2012 is supported between the wheel shaft 2004 and the vehicle body such that it can be oscillated. Reference numeral 2018 denotes a strut, 2020 indicates a toe control rod, 2022 a stabilizer, and 2024 a suspension spring.
When parts are coupled to the bottom surface of the vehicle body by using screws, the screws are usually covered by a cover to protect them from stones or the like. The cover is generally fixed to the vehicle body or the like by welding or the like. If it is necessary to replace the parts on the bottom surface of the vehicle body, the cover must be detached every time, and the work is extremely troublesome.
Such a suspending apparatus for vehicles has been disclosed in JP-A-59-140110. According to the mounting structure of a damper unit for the rear wheels of a vehicle disclosed in this publication, when the rear wheels together with the front wheels are steered, the structure is mounted between the damper unit and the attaching member through a bearing, thereby allowing the damper unit for the rear wheels to be relatively smoothly rotated relative to the vehicle body.
In the suspending apparatus for vehicles, a strut mount cover is attached to the vehicle body side edge portion which is provided for attachment to the strut. An attaching structure of a shock absorber cap has been disclosed in Japanese Utility Model Registration Laid-open No. 60-10167. According to such an attaching structure, a groove portion of the cap is fitted to a projecting portion of a lower seat metal of a cushion rubber and a flange portion which comes into contact with the vehicle body or the like is integrally formed to the outer periphery of the lower portion of the cap.
In the suspending apparatus for vehicles, a wheel shaft is axially connected to a steering knuckle to hold a damper. When the damper, usually a strut-like structure, is inserted into a boss portion of the steering knuckle and is held, a holding bracket is fixedly attached to the outer surface of the strut, thereby providing the function of a positioning device, stopper, or the like. A construction to attach such a bracket to the knuckle has been disclosed in, for instance, Japanese Utility Model Registration Laid-open No. 58-64504. According to such a construction, an annular member covering an outer shell, a clamping member to join and hold the knuckle, and a reinforcement rib are integrally formed.
However, in the conventional suspending apparatus for vehicles, as shown in FIG. 21, an oscillating center line C.sub.1 passes through the axial centers of first and second supporting pins 1040 and 1042 of the first and second vehicle body side supporting portions 1034 and 1036, which are attached to first and second vehicle body side arm portions 1030 and 1032. The centerline C.sub.1 perpendicularly crosses the rotational axis C.sub.2 of the wheel shaft 1008. Therefore, the supporting portions 034 and 1036 are located on the central side of the vehicle body 1002. A concave portion 1062 needs to be formed in a corner portion 1038a of a fuel tank 1038 so that the side of the vehicle body 1002 does not come into contact with, that is, interfere with the first vehicle body side supporting portion 1034. Consequently, the shape of the corner portion 1038a of the fuel tank 1038 becomes complicated, causing problems in that the manufacturing processes become complicated, the costs rise, and the capacity of the fuel tank 1038 decreases. To solve such problems, if the length of the first arm portion 1030 of the suspension arm 1006 is reduced, other problems occur such that steering stability and riding feeling deteriorate, oscillation and noises increase, and the suspending performance deteriorates. Therefore, improvement is desirable.
In the conventional suspending apparatus for vehicles, at least one of the attaching end portions of the first arm member (extending from the attaching position of the wheel on the lower arm to the rear side) and the second arm member (extending contrarily from the attaching position of the wheel to the front side) is constructed by a pin or bush and a bracket. If a large external force is applied to the lower arm from the front direction of the vehicle body due to a collision, since the first arm member is fixed to the vehicle body by the bush, the bush of the first arm member does not support the load caused by the large external force in terms of the construction.
Therefore, when an external force is applied due to a collision from the front or rear direction of the vehicle body, the vehicle body is largely deformed and the load in the direction of the rotary shaft of the first arm member is not supported, so that there occurs a problem such that the bush comes out of the bracket. The lower arm is not deformed at all by a collision, as compared with the deformation of the vehicle body, so that it will be obvious that the lower arm does not absorb the energy upon collision. Thus, the vehicle body absorbs substantially all of the energy upon collision, and the vehicle body is largely deformed.
In FIGS. 22 to 29, the suspension arm 2012 comprises a base plate 2026 and a subplate 2028 for reinforcement as shown in FIGS. 22 to 28. The base plate 2026 is formed so as to have an almost C-shaped cross section by a flat plate portion 2030 and side wall portions 2032 which are arranged on both sides of the flat plate portion 2030 so as to face them. Fixing side edges 2028a of the subplate 2028 are fixedly attached by welding portions 2034 to edges 2032a of the opposite side wall portions 2032 of the base plate 2026, respectively. Thus, as shown in FIG. 22, the suspension arm 2012 is formed in a manner such that the fixing side edges 2028a of the subplate 2028 for reinforcement are fixedly attached to the edges 2032a of the opposite side wall portions 2032 of the C-shaped base plate 2026.
Japanese Utility Model Registration Laid-open No. 61-11406, discloses a suspension arm in which both edge portions of a pair of base plates each having an almost C-shaped cross section are fixedly attached so as to face each other, thereby forming a cylinder body. A subplate for reinforcement is fixedly attached between both of the edge portions. On the other hand, Japanese Utility Model Registration Laid-open Publication No. 62-1761 discloses a suspension arm constructed from two base plates by making the shapes of respective portions thereof different so that the structure of the arm corresponds to different loads acting on the respective portions thereof.
However, in the suspension arm 2012 shown in FIGS. 23 to 25, since the cross section of the suspension arm 2012 at an edge 2028b on the free side of the subplate 2028 changes, there is a problem in that a concentration of stress is caused. To solve such a problem, as shown in FIGS. 26 to 28, there has been proposed the suspension arm 2012' in which a change in cross section is reduced by providing a curved cutting portion 2036 for the free side edge 2028b of the subplate 2028. However, even if the cutting portion 2036 is provided for the free side edge 2028b of the subplate 2028, since the cross section cannot be changed so as to be gradually reduced, there is a problem in that the concentration of stress cannot be sufficiently reduced. There is also a problem in that a concentration of stress is caused in the portion of the free side edge 2028b due to thermal influence by the welding portions 2034 of the base plate 2026 and subplate 2028.
In the conventional suspending apparatus for vehicles, as shown in FIGS. 30 and 31, an outer diameter of the portion of a lower edge 3110b of a strut 3110 is equal to outer diameters of the other portions of the strut 3110. Therefore, attaching the portion of the lower edge 3110b of the strut 3110 to the knuckle 3120 is difficult, and such a structure is practically disadvantageous. When the portion of the lower edge 3110b of the strut 3110 is attached to a knuckle 3120, a portion of an upper edge 3110a of the strut 3110, that is, a strut mount 3118 largely projects into a vehicle body 3102 as shown in FIG. 30.
Therefore, when the strut 3110 is used on the rear side, the strut 3110 largely protrudes into the vehicle body interior. Thus, there are problems such that the angle of inclination of the back seat must decrease, the width of the back seat must be small, and the space in the interior for a baggage chamber or the like decreases. Thus, the interior space cannot be effectively used. On the other hand, when the strut 3110 is used on the front of a vehicle, the strut mount 3118 of the upper edge 3110a of the strut 3110 projects into the vehicle engine compartment, so that the available space in the engine compartment is reduced and cannot be effectively used. Further, since the strut 3110 projects into the vehicle body 3102, there is a problem of large danger. In addition, if the portion of the upper edge 3110a of the strut 3110 is covered, the projecting amount further increases.
In the conventional suspending apparatus for vehicles as shown in FIG. 32, a strut mount 4028 is supported by first and second supporting members 4030 and 4032 from the outside and the inside, respectively, and projects through the side of a vehicle body 4004. An attaching portion 4020, which penetrates the strut mount 4028 and also projects through the side of the vehicle body 4004, is provided in one edge portion of a strut 4012. A cover 4134 covers only the edge portion of the attaching portion 4020 which projects through the side of the vehicle body 4004. Although the cover 4134 shown in FIG. 32 is small and has a small manufacturing cost, since the strut 4012 and cover 4134 integrally vibrate in association with the vibration and noises on the side of the strut 4012, the vibration and noises on the side of the strut 4012 are enhanced and such a structure is practically disadvantageous.
On the other hand, a cover 4234 shown in FIG. 33 is attached to the vehicle body 4004 in order to cover the attaching portion 4020 of the strut 4012 projecting through the vehicle body 4004 and the strut mount 4028 projecting through the vehicle body 4004. Although the cover 4234 can avoid the problems of the cover 4134 shown in FIG. 32, it is large, so as to cover both the attaching portion 4020 of the strut 4012 projecting through the vehicle body 4004 and the strut mount 4028. Consequently, due to the increased size of the cover 4234, the manufacturing cost increases.
In the conventional suspending apparatus for vehicles, the strut does not have a supporting structure from which it may be hung or supported when the outer surface of the strut is subjected to a surface treatment such as coating, plating, or the like. Consequently, the surface treating work is troublesome. If a supporting member such as a bracket or the like is attached to the strut, the number of parts increases and the apparatus becomes more expensive.